The object of the present invention is the protection of building surfaces through the application of hydrophilic polymeric systems to the surfaces of building materials, such as concrete, brick and marble, without changing their appearance. Building surfaces, including painted surfaces, are often porous, difficult to clean and subject to defacement with graffiti. Such surfaces may comprise a wide variety of materials including plaster, masonry, concrete, metal, or wood, and may be coated with typical commercial paints including water-based and oil-based paints such as water-based latexes, water-based enamels, the alkyds, the acrylics, the masonry paints, among others. It is the object of the present invention to provide polymers which can maintain good adhesion to concrete, masonry and paint even when wet, and which can seal or coat such painted or unpainted surfaces to preserve their appearance and integrity, protect them from environmental staining agents and acid rain, and to allow for the removal of graffiti and dirt.
The coating of building materials with hydroxyethyl acrylate monomer and polymerizing the same in place is described in Affleck U.S. Pat. No. 2,827,397. Belgium Pat. No. 780,838 and German Offenlegungsschrift No. P 2211999.9 disclose pre-forming a homopolymer of a hydroxy lower alkyl acrylate or methacrylate or a copolymer thereof with certain copolymerizable monomers, including lower alkyl acrylates and methacrylates, e.g., up to hexyl acrylate.
The problems of lack of extended durability to weathering and to graffiti attacks due to insufficient polymer cure and of obtaining adequate adhesion to the building material were addressed by Jonas Weiss et al. U.S. Pat. No. 4,141,755. Weiss disclosed copolymers of 98-50 percent weight of hydroxy lower alkyl acrylates or methacrylates wherein the alkyl group has 2-3 carbon atoms with 2 to 50 percent weight of stearyl methacrylate or stearyl acrylate. The preferred composition disclosed in the Weiss patent is commercially available under the name of Hydron.RTM.-300. Hydron-300 comprises a copolymer of 90% hydroxyethyl methacrylate ("HEMA") and 10% stearyl methacrylate ("SMA"), cured in situ by the addition of ammonium dichromate, just before application. The stearyl methacrylate provides for better adhesion of the copolymer when wet, especially to limestone, to marble, to glazed ceramic tile and to glazed brick. In addition, dirt removal from surfaces treated with the stearyl methacrylate copolymer is easier than with the coating products available at that time.
Currently, however, because of increasing concerns regarding air pollution and its effects on our environment, the EPA recently instituted regulatory constraints on the Volatile Organic Compound ("V.O.C.") level present in industrial coating solutions. Various states have instituted regulations regarding these levels. For example, New York and New Jersey have implemented regulations prohibiting V.O.C.'s exceeding 45%. The commercially available Hydron.RTM.-300 product contains approximately 92% V.O.C. which greatly exceeds the maximum allowable level of 45%. The present invention relates to a reformulation of a commercially available polymeric coating solution to include a large amount of water, in order to comply with EPA standards. Because the Hydron.RTM.-300 polymer is not water soluble, and only hydrophilic enough to be mixed with small levels of water before precipitating out of solution, the present invention addresses this problem by altering the polymeric composition of Hydron.RTM.-300 in order to render it more water compatible.